Disc brake rotor adapter, disc brake rotor including adapter, magnetism generation device

ABSTRACT

A magnetism generation device is attachable to a disc brake rotor adapter for a bicycle hub. The magnetism generation device comprises a magnetism generation portion and a holder. The holder has a first portion and a second portion. The first portion supports the magnetism generation portion. The second portion is releasably attached to the first portion with a portion of the disc brake rotor adapter disposed between the first and second portions while the magnetism generation device in an installed state on the disc brake rotor adapter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuing application of U.S. application Ser.No. 15/866,621 filed on Jan. 10, 2018. The entire disclosure of U.S.application Ser. No. 15/866,621 is hereby incorporated herein byreference. This application claims priority to Japanese PatentApplication No. 2017-04720, filed on Jan. 13, 2017 and Japanese PatentApplication No. 2017-022141, filed on Feb. 9, 2017. The entiredisclosures of Japanese Patent Application Nos. 2017-04720 and2017-022141 are hereby incorporated herein by reference.

BACKGROUND Field of the Invention

The present invention relates to a disc brake rotor adapter, a discbrake rotor including an adapter, and a magnetism generation device.

Background Information

A technique for detecting a rotational state of a wheel is known. Forexample, Japanese Laid-Open Patent Publication No. 10-076988 (patentdocument 1) discloses a technique to detect a wheel rotational state. Inparticular, the patent document 1 discloses a sensor that detects amagnet attached to a spoke of a wheel to detect the rotational state ofthe wheel.

SUMMARY

One object of the present invention is to provide a disc brake rotoradapter that is preferably used to detect a rotational state of abicycle wheel, a disc brake rotor including the adapter, and a magnetismgeneration device.

In accordance with a first aspect of the present invention, a magnetismgeneration device is attachable to a disc brake rotor adapter for abicycle hub. The magnetism generation device comprises a magnetismgeneration portion and a holder. The holder has a first portion and asecond portion. The first portion supports the magnetism generationportion. The second portion is releasably attached to the first portionwith a portion of the disc brake rotor adapter disposed between thefirst and second portions while the magnetism generation device in aninstalled state on the disc brake rotor adapter.

In accordance with a second aspect of the present invention, a magnetismgeneration device comprises a magnetism generation portion, an attachingportion and a fastener. The attaching portion supports the magnetismgeneration portion. The fastener is configured to secure the attachingportion on a portion of the disc brake rotor adapter while the magnetismgeneration device is in an installed state on the disc brake rotoradapter.

Accordingly, the disc brake rotor adapter, the disc brake rotorincluding the adapter, and the magnetism generation device arepreferably used to detect a rotational state of a bicycle wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings, which form a part of thisoriginal disclosure.

FIG. 1 is a side elevational view of a bicycle hub having a disc brakerotor, which includes a disc brake adapter, and a bicycle magnetismgeneration device in accordance with a first embodiment as views in afirst direction.

FIG. 2 is an exploded front elevational view of the bicycle hub and thedisc brake rotor having the disc brake adapter shown in FIG. 1.

FIG. 3 is a partially cross-sectional view of the disc brake rotor andthe disc brake adapter taken along section line 3-3 in FIG. 1.

FIG. 4 is a side elevational view of the disc brake adapter with thebicycle magnetism generation device as viewed in the first direction inFIG. 1.

FIG. 5 is a side elevational view of the disc brake adapter with thebicycle magnetism generation device as viewed in a second direction inFIG. 1.

FIG. 6 is a cross-sectional view of the disc brake adapter taken alongsection line 6-6 in FIG. 5.

FIG. 7 is a side elevational view of a disc brake adapter having abicycle magnetism generation device in in accordance with a secondembodiment as viewed in the second direction.

FIG. 8 is a cross-sectional view of the disc brake adapter having abicycle magnetism generation device taken along section line 8-8 in FIG.7.

FIG. 9 is a side elevational view of a disc brake adapter having abicycle magnetism generation device in accordance with a thirdembodiment as viewed in the second direction.

FIG. 10 is an enlarged, partial cross-sectional view of the disc brakeadapter and the bicycle magnetism generation device taken along sectionline 10-10 in FIG. 9.

FIG. 11 is a side elevational view of a disc brake adapter having abicycle magnetism generation device in accordance with a fourthembodiment as viewed in the second direction.

FIG. 12 is a cross-sectional view of the disc brake adapter and thebicycle magnetism generation device taken along section line 12-12 inFIG. 11.

FIG. 13 is a side elevational view of a disc brake adapter having abicycle magnetism generation device in accordance with a fifthembodiment as viewed in the second direction.

FIG. 14 is a cross-sectional view of the disc brake adapter and thebicycle magnetism generation device taken along section line 14-14 inFIG. 13.

FIG. 15 is an enlarged, partial cross-sectional view of a modified discbrake adapter in accordance with a modification of the fifth embodiment.

FIG. 16 is an enlarged, partial cross-sectional view of a disc brakeadapter having a bicycle magnetism generation device in accordance witha sixth embodiment.

FIG. 17 is an enlarged, partial cross-sectional view of a modified discbrake adapter having a bicycle magnetism generation device in accordancewith a modification of the sixth embodiment.

FIG. 18 is an enlarged, partial cross-sectional view of a disc brakeadapter having a bicycle magnetism generation device in accordance witha seventh embodiment.

FIG. 19 is an enlarged, partial cross-sectional view of a disc brakeadapter having a bicycle magnetism generation device in accordance witha modification of the seventh embodiment.

FIG. 20 is an enlarged, partial cross-sectional view of a disc brakeadapter having a bicycle magnetism generation device in accordance withan eighth embodiment.

FIG. 21 is a side elevational view of a disc brake adapter in accordancewith a first modification as viewed in the second direction.

FIG. 22 is a side elevational view of a disc brake adapter in accordancewith a second modification as viewed in the second direction.

FIG. 23 is a side elevational view of an attaching portion of a discbrake adapter in accordance with a third modification as viewed in thefirst direction.

FIG. 24 is a side elevational view of a disc brake adapter in accordancewith a fourth modification as viewed in the second direction.

FIG. 25 is a side elevational view of a disc brake adapter in accordancewith a fifth modification as viewed in the second direction.

FIG. 26 is a cross-sectional view of a disc brake adapter taken alongsection line 26-26 in FIG. 25.

FIG. 27 is an enlarged, partial cross-sectional view of a disc brakerotor in accordance with a sixth modification.

FIG. 28 is an exploded perspective view of a disc brake rotor inaccordance with a seventh modification.

FIG. 29 is a perspective view of a disc brake rotor in accordance withan eighth modification.

FIG. 30 is a perspective view of an attaching portion of the disc brakerotor shown in FIG. 29.

FIG. 31 is an exploded perspective view of a disc brake rotor inaccordance with a ninth modification.

DETAILED DESCRIPTION OF EMBODIMENTS

Selected embodiments will now be explained with reference to thedrawings. It will be apparent to those skilled in the bicycle field fromthis disclosure that the following descriptions of the embodiments areprovided for illustration only and not for the purpose of limiting theinvention as defined by the appended claims and their equivalents.

First Embodiment

A disc brake rotor 10 that includes a first embodiment of an adapter 20Awill now be described with reference to FIGS. 1 to 13.

As shown in FIG. 1, the disc brake rotor 10 includes the adapter 20A anda main body 12 that is coupled to the adapter 20A.

As shown in FIG. 2, the disc brake rotor 10 is fixed to a bicycle hub Hby a fixing member R, which fixes the adapter 20A to the bicycle hub H(simply referred to as hub H). The hub H includes a hub shell H1, whichrotates integrally with the disc brake rotor 10. The fixing member R hasa fixing function that fixes the adapter 20A to the hub H. Morespecifically, the hub H has an outer circumference with a plurality offirst splines H3 that mate with a plurality of second splines 32A of thedisc brake rotor 10. With the second splines 32A engaged with the firstsplines H3, the disc brake rotor 10 is held between the hub H and thefixing member R. In this way, the disc brake rotor 10 is non-rotatablycoupled to the hub H. The hub shell H1 of the hub H has a first end H4in a direction that extends along a rotational axis of the hub H. Thefirst splines H3 are provided on the first end H4. The first splines H3include ridges and valleys that extend in the direction extending alongthe rotational axis of the hub H. A projection H5 is formed on an outercircumference of the hub shell H1 adjacent to the first splines H3. Theprojection H5 is located closer to a second end H6 of the hub shell H1than the first splines H3 in the direction extending along therotational axis of the hub H. The projection H5 projects to an outerside of the first splines H3 in a radial direction of the hub H. It ispreferred that the projection H5 be formed on the entire circumferenceof the hub shell H1. In FIG. 2, the hub H does not include a freewheel.However, the hub H can include a freewheel.

The fixing member R includes a disc-shaped discoid portion R1 and aprojection R2, which projects from the discoid portion R1 in an axialdirection of the disc brake rotor 10. In the description hereafter, theaxial direction of the disc brake rotor 10 is simply referred to as “theaxial direction.” The projection R2 has an outer circumference includingan externally-threaded part R3. As shown in FIG. 3, theexternally-threaded part R3 of the projection R2 is configured to befastened to an internally-threaded part H2, which is formed on an innercircumference of the hub shell H1 of the hub H. In a case where theouter circumference of the hub shell H1 of the hub H includes anexternally-threaded part that fastens the fixing member R, theprojection R2 can be omitted from the fixing member R. In this case, aninner circumference of the discoid portion R1 includes aninternally-threaded part configured to be fastened to the externalthreaded part, which is formed on the outer circumference of the hubshell H1.

As shown in FIG. 1, the main body 12 is discoid. The main body 12includes a pair oppositely facing slide surfaces 12A, which are slidableon brake pads (not shown) of a disc brake caliper. As shown in FIG. 2,the slide surfaces 12A are defined by opposite side surfaces 12S of themain body 12 in the axial direction. The main body 12 is annular. Theslide surfaces 12A are formed on outer circumferences of the main body12. As shown in FIG. 3, second holes 12B extend through the main body 12in the vicinity of an inner circumference of the main body 12 in adirection parallel to the axial direction. It is preferred that throughholes 12D extend through each of the outer circumference and the innercircumference of the main body 12 and an intermediate portion of themain body 12, which is located between the outer circumference and theinner circumference, in the direction parallel to the axial direction.It is preferred that the intermediate portion include a plurality ofarms 12C. The arms 12C are spaced apart from one another in acircumferential direction and outwardly extend in a radial direction ofthe disc brake rotor 10. In the description hereafter, the radialdirection of the disc brake rotor 10 is simply referred to as “theradial direction.”

The adapter 20A is configured to attach the main body 12 of the discbrake rotor 10 to the hub H (refer to FIG. 2) of a bicycle. As shown inFIG. 4, the adapter 20A includes an adapter main body 22, a magnetismgeneration portion 24 and an attaching portion 26. In one example, theadapter 20A further includes a thermal insulation portion 28 (refer toFIG. 6) and fastening portions 30.

The adapter main body 22 is formed from a metal. The adapter main body22 includes steel or an aluminum alloy. It is preferred that the adaptermain body 22 be formed from a low permeability material. The adaptermain body 22 includes an inner portion 32 and an outer portion 34. Theinner portion 32 includes the second spline 32A. The second spline 32Ais configured to be engaged with the first spline H3, which is providedon the hub H shown in FIG. 2. The inner portion 32 has one end 32B inthe axial direction. In a state where the disc brake rotor 10 is coupledto the hub H, the one end 32B is in contact with the projection H5 ofthe hub shell H1. It is preferred that the end surface of the one end32B of the inner portion 32 in the axial direction be included in aplane that is orthogonal to the axial direction. As shown in FIG. 1, theouter portion 34 is located at a radially outer side of the innerportion 32. The main body 12 of the disc brake rotor 10 is coupled tothe outer portion 34. The outer portion 34 includes a plurality ofprojections 36, which project outward in the radial direction. The mainbody 12 of the disc brake rotor 10 is coupled to the projections 36. Theprojections 36 are provided at predetermined intervals in thecircumferential direction of the disc brake rotor 10. In the descriptionhereafter, the circumferential direction of the disc brake rotor 10 issimply referred to as “the circumferential direction.” The number ofprojections 36 is, for example, six. As shown in FIG. 3, each of theprojections 36 includes a first hole 36A, which is used for attachmentof the main body 12 of the disc brake rotor 10. The first holes 36Aextend in a direction parallel to the axial direction. The first holes36A are formed in the distal end of each projection 36. It is preferredthat the first holes 36A extend through the projections 36 in the axialdirection. The first holes 36A are formed in positions corresponding tothe second holes 12B, which are formed in the main body 12 of the discbrake rotor 10. The fastening portions 30 are inserted into the firstholes 36A and the second holes 12B. The fastening portions 30 include,for example, rivets. The fastening portions 30 fasten the main body 12of the disc brake rotor 10 and the adapter 20A to each other. Thefastening portions 30 can include bolts. In a case where the fasteningportions 30 include bolts, the second holes 12B are, for example,defined by threaded wall surfaces configured to be coupled to the bolts.With the bolts inserted into the second holes 12B, the main body 12 isheld between the head of each bolt and the corresponding projection 36.This fixes the main body 12.

The attaching portion 26 attaches the magnetism generation portion 24 tothe adapter main body 22 in a manner irrelevant to the fixing functionof the fixing member R. The attaching portion 26 is provided between twoof the projections 36 that are adjacent to each other in thecircumferential direction. As shown in FIG. 6, the attaching portion 26is formed integrally with the adapter main body 22. The attachingportion 26 includes a holder 38, which holds the magnetism generationportion 24. The holder 38 includes a recess 38A (e.g., an opening). Therecess 38A is open at one side in the axial direction. In a state wherethe disc brake rotor 10 is coupled to the hub H, the opening of therecess 38A is located toward the second end H6 of the hub shell H1 ofthe hub H. In this case, it is preferred that the adapter main body 22be formed from a low permeability material such as an aluminum alloy. Ina case where the adapter main body 22 is formed from a low permeabilitymaterial, the opening of the recess 38A can be formed at a radiallyouter side with the disc brake rotor 10 coupled to the hub H. In a statewhere the adapter main body 22 couples the disc brake rotor 10 to thehub H, the opening of the recess 38A can be located at a side oppositeto the second end H6 of the hub shell H1 of the hub H. In a case wherethe adapter main body 22 is formed from a high permeability material, itis preferred that the opening of the recess 38A be located at the sideopposite to the second end H6 of the hub shell H1 of the hub H with thedisc brake rotor 10 coupled to the hub H.

The magnetism generation portion 24 is accommodated in the recess 38A.It is preferred that the entire magnetism generation portion 24 beaccommodated in the recess 38A. However, the magnetism generationportion 24 can partially project from the recess 38A. The magnetismgeneration portion 24 includes at least one permanent magnet. Themagnetism generation portion 24 is provided between two adjacent ones ofthe projections 36. Although there is no limitation on the shape of thepermanent magnet, the permanent magnet is, for example, tubular. Thepermanent magnet is provided in the recess 38A so that magnetic polesare located next to one another in the axial direction. The magnetismgeneration portion 24 is provided between two of the projections 36 thatare adjacent to each other in the circumferential direction. The thermalinsulation portion 28 is located between the magnetism generationportion 24 and the attaching portion 26 to limit heat transfer. In oneexample, the thermal insulation portion 28 includes a resin. It ispreferred that the thermal insulation portion 28 be formed from a lowpermeability material. The thermal insulation portion 28 and themagnetism generation portion 24 are held in the recess 38A through lightpress-fitting or by an adhesive. The magnetism generation portion 24 canbe molded by a resin.

Second Embodiment

A second embodiment of an adapter 20B will now be described withreference to FIGS. 7 and 8. The adapter 20B of the second embodiment isthe same as the adapter 20A of the first embodiment except that theadapter 20B includes an attaching portion 42 that is formed separatelyfrom the adapter main body 22. The same reference characters are givento those elements that are the same as the corresponding elements of thefirst embodiment. Such elements will not be described in detail.

As shown in FIG. 7, the attaching portion 42 is provided between twoadjacent ones of the projections 36. The attaching portion 42 is formedseparately from the adapter main body 22. The attaching portion 42attaches the magnetism generation portion 24 to the adapter main body 22in a manner irrelevant to the fixing function of the fixing member R.The attaching portion 42 includes a holder 44 and an engagement portion46. The holder 44 is formed from a metal or a resin. It is preferredthat the holder 44 be formed from a low permeability material. Theholder 44 includes a recess 44A. The recess 44A is open at one side inthe axial direction. In a state where the disc brake rotor 10 is coupledto the hub H, the opening of the recess 44A is located toward the secondend H6 of the hub shell H1 of the hub H. In a state where the disc brakerotor 10 is coupled to the hub H, the opening of the recess 44A can beformed at a side opposite to the second end H6 of the hub shell H1 ofthe hub H. In a case where the holder 44 is formed from a highpermeability material, it is preferred that the opening of the recess44A be formed at the side opposite to the second end H6 of the hub shellH1 of the hub H with the disc brake rotor 10 coupled to the hub H. Theengagement portion 46 engages the adapter main body 22. The engagementportion 46 includes, for example, an adhesive. The engagement portion 46fixes the holder 44 to the outer portion 34. In a case where the holder44 is formed from a low permeability material such as an aluminum alloyor a resin, the opening of the recess 44A can be formed at an outer sideor an inner side in the radial direction.

As shown in FIG. 8, the magnetism generation portion 24 is accommodatedin the recess 44A. It is preferred that the entire magnetism generationportion 24 be accommodated in the recess 44A. However, the magnetismgeneration portion 24 can partially project from the recess 44A. Theholder 44 and the engagement portion 46 limit heat transfer between theadapter main body 22 and the magnetism generation portion 24. Since theattaching portion 42 functions as a heat insulation portion, the thermalinsulation portion 28 of the first embodiment can be omitted from theadapter 20B of the second embodiment. However, the thermal insulationportion 28 can be provided between the attaching portion 42 and themagnetism generation portion 24.

Third Embodiment

A third embodiment of an adapter 20C will now be described withreference to FIGS. 9 and 10. The adapter 20C of the third embodiment isthe same as the adapter 20A of the first embodiment except that at leastone of the fastening portions 30 is changed to a joining portion 54, themagnetism generation portion 24 is provided on one of the projections36, and the adapter 20C includes an attaching portion 48 that is formedseparately from the adapter main body 22. The same reference charactersare given to those elements that are then same as the correspondingelements of the first embodiment. Such elements will not be described indetail.

As shown in FIG. 9, the attaching portion 48 is provided on one of theprojections 36. The attaching portion 48 attaches the magnetismgeneration portion 24 to the adapter main body 22 in a manner irrelevantto the fixing function of the fixing member R. The attaching portion 48is formed separately from the adapter main body 22. The attachingportion 48 includes a holder 50. In one example, the attaching portion48 further includes the joining portion 54. The joining portion 54includes a rivet in the same manner as the fastening portions 30. Theholder 50 is formed from a metal or a resin. In a state where the discbrake rotor 10 is coupled to the hub H, the holder 50 is located towardthe second end H6 of the hub shell H1 of the hub H. The holder 50includes a recess 50A. In a state where the disc brake rotor 10 iscoupled to the hub H, the opening of the recess 50A is formed toward thesecond end H6 of the hub shell H1 of the hub H. A through hole 50Bextends through the bottom of the recess 50A toward the adapter mainbody 22. The magnetism generation portion 24 and the joining portion 54are located at positions that overlap with each other in the axialdirection. In another example, the magnetism generation portion 24 andthe joining portion 54 are located at positions that do not overlap witheach other in the axial direction. In this case, the holder 50 extendsfor example, radially inward or outward from the joining portion 54 oreither side in the axial direction. The recess 50A is formed in aposition that does not overlap the joining portion 54.

The attaching portion 48 is inserted into one of the first holes 36A andfixed to the corresponding one of the projections 36. As shown in FIG.10, the joining portion 54 is inserted into the first hole 36A and oneof the second holes 12B, which are formed in the main body 12 of thedisc brake rotor 10, to join the projection 36 and the main body 12 ofthe disc brake rotor 10. The joining portion 54 has a first end 54A,which is inserted through the through hole 50B and located in the cavityof the recess 50A. The holder 50 is held between the projection 36 and aportion of the first end 54A located in the cavity of the recess 50A.This supports the holder 50.

The magnetism generation portion 24 is accommodated in the recess 50A.It is preferred that the entire magnetism generation portion 24 beaccommodated in the recess 50A. However, the magnetism generationportion 24 can partially project from the recess 50A. The magnetismgeneration portion 24 is provided on the projection 36. The thermalinsulation portion 28 is located between the magnetism generationportion 24 and the attaching portion 48 to limit heat transfer.

Fourth Embodiment

A fourth embodiment of an adapter 20D will now be described withreference to FIGS. 11 and 12. The adapter 20D of the fourth embodimentis the same as the adapter 20A of the first embodiment except that theadapter 20D includes an attaching portion 56 that is fixed to one of theprojections 36, and the attaching portion 56 is formed separately fromthe adapter main body 22. The same reference characters are given tothose elements that are the same as the corresponding elements of thefirst embodiment. Such elements will not be described in detail.

As shown in FIG. 11, the attaching portion 56 is provided on one of theprojections 36. The attaching portion 56 attaches the magnetismgeneration portion 24 to the adapter main body 22 in a manner irrelevantto the fixing function of the fixing member R. The attaching portion 56is formed separately from the adapter main body 22. The attachingportion 26 is configured to be attachable to and removable from theadapter main body 22. The attaching portion 56 includes a holder 58 andan engagement portion 60 (refer to FIG. 12). The holder 58 includes arecess 58A. The holder 58 is formed from a metal or a resin. In a statewhere the disc brake rotor 10 is coupled to the hub H, the holder 58 islocated toward the second end H6 of the hub shell H1 of the hub H. In astate where the disc brake rotor 10 is coupled to the hub H, the openingof the recess 58A is located toward the second end H6 of the hub shellH1 of the hub H. In this case, it is preferred that the holder 58 beformed from a low permeability material such as an aluminum alloy or aresin. In another example, in a state where the disc brake rotor 10 iscoupled to the hub H, the holder 58 is located at a side opposite to thesecond end H6 of the hub shell H1 of the hub H. In a state where thedisc brake rotor 10 is coupled to the hub H, the opening of the recess58A is located at the side opposite to the second end H6 of the hubshell H1 of the hub H. In a case where the holder 58 is formed from alow permeability material such as an aluminum alloy or a resin, theopening of the recess 58A can be formed at one of a radially inner side,a radially outer side, and one side or the other side in thecircumferential direction. The magnetism generation portion 24 isaccommodated in the recess 58A. It is preferred that the entiremagnetism generation portion 24 be accommodated in the recess 58A.However, the magnetism generation portion 24 can partially project fromthe recess 58A. The thermal insulation portion 28 is located between themagnetism generation portion 24 and the holder 58 to limit heattransfer.

As shown in FIG. 12, the engagement portion 60 includes a first threadedpart 60A. The adapter main body 22 includes a second threaded part 22B,which engages the first threaded part 60A. The first threaded part 60Ais externally threaded. The second threaded part 22B is internallythreaded. The second threaded part 22B is formed in one of theprojections 36 at an inner side of the first hole 36A in the radialdirection. The threaded hole of the second threaded part 22B extendsparallel to the axial direction. In a state where the disc brake rotor10 is coupled to the hub H, the threaded hole is open toward the secondend H6 of the hub shell H1 of the hub H. In a case where the holder 58is located at a side opposite to the second end H6 of the hub shell H1,the threaded hole of the second threaded part 22B is open toward theside opposite to the second end H6 of the hub shell H1. The threadedhole of the second threaded part 22B can extend parallel to the axialdirection through the projection 36. The engagement portion 60 can beformed integrally with the holder 58. Alternatively, the engagementportion 60 can be formed separately from the holder 58 and coupled tothe holder 58. The first threaded part 60A is fastened to the secondthreaded part 22B to couple the magnetism generation portion 24 to theadapter main body 22. The threaded hole of the second threaded part 22Bcan extend in a direction that intersects the axial direction.

Fifth Embodiment

A fifth embodiment of an adapter 20E will now be described withreference to FIGS. 13 and 14. The adapter 20E of the fifth embodiment isthe same as the adapter 20A of the first embodiment except that theadapter 20E includes an attaching portion 62 that is fixed to one of theprojections 36, and the attaching portion 62 is formed separately fromthe adapter main body 22. The same reference characters are given tothose elements that are the same as the corresponding elements of thefirst embodiment. Such elements will not be described in detail.

As shown in FIG. 13, the attaching portion 62 is provided on one of theprojections 36. The attaching portion 62 attaches the magnetismgeneration portion 24 to the adapter main body 22 in a manner irrelevantto the fixing function of the fixing member R. The attaching portion 62is formed separately from the adapter main body 22. The attachingportion 62 is configured to be attachable to and removable from theadapter main body 22. The attaching portion 62 includes a holder 64 andan engagement portion 66 (refer to FIG. 14). The holder 64 includes arecess 64A. The holder 64 is formed from a metal or a resin. In a statewhere the disc brake rotor 10 is coupled to the hub H, the holder 64 islocated toward the second end H6 of the hub shell H1 of the hub H. In astate where the disc brake rotor 10 is coupled to the hub H, the openingof the recess 64A is located toward the second end H6 of the hub shellH1 of the hub H. In this case, it is preferred that the holder 64 beformed from a low permeability material such as an aluminum alloy or aresin. In another example, in a state where the disc brake rotor 10 iscoupled to the hub H, the opening of the recess 64A is formed at a sideopposite to the second end H6 of the hub shell H1 of the hub H. In acase where the holder 64 is formed from a low permeability material suchas an aluminum alloy or a resin, the opening of the recess 64A can beformed at one of a radially inner side, a radially outer side, and oneside or the other side in the circumferential direction. In a statewhere the disc brake rotor 10 is coupled to the hub H, the holder 64 canbe located at the side opposite to the second end H6 of the hub shell H1of the hub. The magnetism generation portion 24 is accommodated in therecess 64A. It is preferred that the entire magnetism generation portion24 be accommodated in the recess 64A. However, the magnetism generationportion 24 can partially project from the recess 64A.

As shown in FIG. 14, the engagement portion 66 includes two hooks 66A,which extend from the holder 64 in the axial direction. One of the twohooks 66A is inserted into one of through holes 22C, which extendthrough the projections 36. The other one of the two hooks 66A islocated at an outer side of the projection 36 in the circumferentialdirection. The projection 36 is held between the two hooks 66A. Thisfixes the holder 64 to the projection 36. The engagement portion 66 canbe formed separately from the hooks 66A and coupled to the hooks 66A.Alternatively, the engagement portion 66 can be formed integrally withthe hooks 66A.

As shown in FIG. 15, instead of the engagement portion 66, the attachingportion 62 can include an engagement portion 68 that has one end 68A andthe other end 68B in the circumferential direction and is annular withthe one end 68A coupled to the other end 68B. In a state where the oneend 68A is separated from the other end 68B, the projection 36 isengaged with an inner side of the engagement portion 68. Then, the oneend 68A is coupled to the other end 68B to fix the holder 64 to theprojection 36. The one end 68A and the other end 68B include a recessand a projection that engage with each other.

Sixth Embodiment

A sixth embodiment of an adapter 20F will now be described withreference to FIG. 16. The adapter 20F of the sixth embodiment is thesame as the adapter 20E of the fifth embodiment except that a holder 72and engagement portions 74 are separate from each other. The samereference characters are given to those elements that are the same asthe corresponding elements of the fifth embodiment. Such elements willnot be described in detail.

An attaching portion 70 includes the holder 72 and the engagementportions 74. The attaching portion 70 attaches the magnetism generationportion 24 to the adapter main body 22 in a manner irrelevant to thefixing function of the fixing member R. The holder 72 includes a firstportion 76 and a second portion 78, which are located at opposite sidesof the projection 36. In a state where the disc brake rotor 10 iscoupled to the hub H, the first portion 76 is located at a side of theprojection 36 closer to the second end H6 of the hub shell H1 of the hubH. The first portion 76 includes a recess 76A. In a state where the discbrake rotor 10 is coupled to the hub H, the second portion 78 is locatedat a side opposite to the second end H6 of the hub shell H1 of the hubH. In a state where the disc brake rotor 10 is coupled to the hub H, theopening of the recess 76A is located toward the second end H6 of the hubshell H1 of the hub H. In this case, it is preferred that the firstportion 76 be formed from a low permeability material such as analuminum alloy or a resin. In another example, the first portion 76 andthe opening of the recess 76A are located at the side opposite to thesecond end H6 of the hub shell H1, and the second portion 78 is locatedtoward the second end H6 of the hub shell H1. In a case where the holder72 is formed from a low permeability material such as an aluminum alloyor a resin, the opening of the recess 76A can be formed at one of aradially inner side, a radially outer side, and one side or the otherside in the circumferential direction. The magnetism generation portion24 is accommodated in the recess 76A. It is preferred that the entiremagnetism generation portion 24 be accommodated in the recess 76A.However, the magnetism generation portion 24 can partially proj ect fromthe recess 64A. The thermal insulation portion 28 is located between themagnetism generation portion 24 and the attaching portion 70 to limitheat transfer.

The engagement portions 74 are formed separately from the holder 72.Each engagement portion 74 includes a first threaded part 74A. Theengagement portion 74 is formed by a bolt. The holder 72 includes firstthrough holes 76B through which the engagement portions 74 extend, andthird threaded parts 78A engaged with the first threaded parts 74A in astate where the engagement portions 74 extend through the first throughholes 76B. The first through holes 76B are formed in the first portion76. The third threaded parts 78A are formed in the second portion 78.The threaded hole of each third threaded part 78A can extend through thesecond portion 78. The attaching portion 70 includes a plurality ofengagement portions 74. The holder 72 includes the first through holes76B and the third threaded parts 78A in conformance with the number ofthe engagement portions 74. At least two of the engagement portions 74are located at positions where the projection 36 is held between theengagement portions 74 in the circumferential direction. In a statewhere the projection 36 is held between the first portion 76 and thesecond portion 78, the engagement portions 74 extend through the firstthrough holes 76B, and the first threaded parts 74A are fastened to thethird threaded parts 78A. This fixes the attaching portion 70 to theprojection 36.

As shown in FIG. 17, in the adapter 20F, the diameter of each firstthrough hole 76B can be enlarged at the end located closer to the secondend H6 of the hub shell H1 of the hub H so that the end of eachengagement portion 74 will not project from the first portion 76 in astate where the disc brake rotor 10 is coupled to the hub H.Additionally, the recess 76A can be omitted from the first portion 76.The magnetism generation portion 24 and the thermal insulation portion28 can be provided on a surface of the first portion 76 that is oppositeto the projection 36.

Seventh Embodiment

A seventh embodiment of an adapter 20G will now be described withreference to FIG. 18. The adapter 20G of the seventh embodiment is thesame as the adapter 20F of the sixth embodiment except that a holder 80includes the first portion 76 and the second portion 78 that areconnected to each other. The same reference characters are given tothose elements that are the same as the corresponding elements of thesixth embodiment. Such elements will not be described in detail.

The holder 80 includes the first portion 76, the second portion 78, anda third portion 82. The third portion 82 connects an end of the firstportion 76 and an end of the second portion 78 in the circumferentialdirection. The third portion 82 extends parallel to the axial direction.The holder 80 has a U-shaped cross section in a direction orthogonal tothe radial direction. The third portion 82 is located at one side of theprojection 36 in the circumferential direction. The engagement portion74 extends through the first through hole 76B of the first portion 76 atthe other side of the projection 36 in the circumferential direction.The first threaded part 74A is fastened to the third threaded part 78A.

As shown in FIG. 19, in the adapter 20G, the diameter of the firstthrough hole 76B can be enlarged at the end located closer to the secondend H6 of the hub shell H1 of the hub H so that the end of theengagement portion 74 will not project from the first portion 76 in astate where the disc brake rotor 10 is coupled to the hub H.Additionally, the recess 76A can be omitted from the first portion 76.The magnetism generation portion 24 and the thermal insulation portion28 are provided on a surface of the first portion 76 that is opposite tothe projection 36.

Eighth Embodiment

An eighth embodiment of an adapter 20H will now be described withreference to FIG. 20. The adapter 20H of the eighth embodiment is thesame as the adapter 20A of the first embodiment except that the adapter20H includes an attaching portion 84 that is fixed to one of theprojections 36, and the attaching portion 84 is formed separately fromthe adapter main body 22. The same reference characters are given tothose elements that are the same as the corresponding elements of thefirst embodiment. Such elements will not be described in detail.

In the adapter 20H, an engagement portion 88 and a holder 86 are formedseparately from each other. The attaching portion 84 of the adapter 20Hincludes the holder 86 and the engagement portion 88. The attachingportion 84 attaches the magnetism generation portion 24 to the adaptermain body 22 in a manner irrelevant to the fixing function of the fixingmember R. The attaching portion 84 is provided on one of the projections36. The engagement portion 88 includes a first threaded part 88A. Theattaching portion 84 is configured to be attachable to and removablefrom the adapter main body 22. The adapter main body 22 includes asecond through hole 22D through which the engagement portion 88 extends.The second through hole 22D extends in the axial direction. The holder86 includes a fourth threaded part 86B engaged with the first threadedpart 88A in a state where the engagement portion 88 extends through thesecond through hole 22D.

The holder 86 includes a recess 86A. The holder 86 is formed from ametal or a resin. In a state where the disc brake rotor 10 is coupled tothe hub H, the holder 86 is located toward the second end H6 of the hubshell H1 of the hub H. In a state where the disc brake rotor 10 iscoupled to the hub H, the opening of the recess 86A is located towardthe second end H6 of the hub shell H1 of the hub H. In this case, it ispreferred that the holder 86 be formed from a low permeability materialsuch as an aluminum alloy or a resin. In another example, in a statewhere the disc brake rotor 10 is coupled to the hub H, the holder 86 islocated at a side opposite to the second end H6 of the hub shell H1 ofthe hub H. In a state where the disc brake rotor 10 is coupled to thehub H, the opening of the recess 86A is located at the side opposite tothe second end H6 of the hub shell H1 of the hub H. In a case where theholder 86 is formed from a low permeability material, the opening of therecess 86A can be formed at one of a radially inner side, a radiallyouter side, and one side or the other side in the circumferentialdirection. The magnetism generation portion 24 is accommodated in therecess 86A. It is preferred that the entire magnetism generation portion24 be accommodated in the recess 86A. However, the magnetism generationportion 24 can partially project from the recess 86A. The thermalinsulation portion 28 is located between the magnetism generationportion 24 and the holder 86 to limit heat transfer.

The first threaded part 88A is externally threaded. The fourth threadedpart 86B is internally threaded. The engagement portion 88 extendsthrough the second through hole 22D from a side of the holder 86opposite to the projection 36 in the axial direction. The first threadedpart 88A is fastened to the fourth threaded part 86B. This fixes theattaching portion 84 to the projection 36. The engagement portion 88 isformed by a bolt. The projection 36 is held between the head of the boltand the holder 86. This restricts movement of the holder 86 in the axialdirection.

Modifications

The above description illustrates embodiments of a disc brake rotoradapter, a disc brake rotor including the adapter, and a magnetismgeneration device according to the present invention and is not intendedto be restrictive. The disc brake rotor adapter, the disc brake rotorincluding the adapter, and the magnetism generation device according tothe present invention can be modified as follows. Further, two or moreof the modifications can be combined. In the modifications, the samereference characters are given to those elements that are the same asthe corresponding elements of the embodiments. Such elements will not bedescribed in detail.

The attaching portions 62, 70 of the fifth to seventh embodiments can becoupled to the adapter main bodies 22 of the first to fourthembodiments, which do not include the through holes 22C. For example, asshown in FIG. 21, the attaching portion 62 is configured to surround aradially intermediate portion of one of the projections 36 of theadapter main body 22.

The attaching portion 84 that is shown in FIG. 20 can be changed to anattaching portion 90 that includes an annular base 92 and is shown inFIG. 22. The inner diameter of the base 92 is larger than the innerdiameter of the inner portion 32 of the adapter main body 22 and theouter diameter of the fixing member R. It is preferred that the size ofthe outer diameter of the base 92 be selected so that the outercircumference of the base 92 is located at an inner side of thefastening portions 30 in the radial direction. It is preferred that thebase 92 be fixed to two or more of the projections 36 by the engagementportion 88 that is shown in FIG. 20. The magnetism generation portion 24includes a plurality of permanent magnets 24A, which are spaced apartfrom one another in a circumferential direction of the base 92. The base92 includes the recesses 86A, which are spaced apart from one another inthe circumferential direction. The permanent magnets 24A arerespectively accommodated in the recesses 86A.

Instead of fixing the attaching portion 90 to the adapter main body 22with the engagement portion 88 so that the attaching portion 90 isattachable to and removable from the adapter main body 22, as shown inFIG. 23, the attaching portion 90 can be fixed to the adapter main body22 by the same engagement portion 66 as in the fifth embodiment so thatthe attaching portion 90 is attached to and removable from the adaptermain body 22. The hooks 66A, which project toward the adapter main body22 in the axial direction, are provided on a surface of the base 92located toward the adapter main body 22. It is preferred that multiplepairs of hooks 66A be provided. Each pair of the hooks 66A is configuredto be engaged with one of the projections 36.

The magnetism generation portion 24 that is shown in FIG. 22 can bechanged to a magnetism generation portion 94 that includes an annularpermanent magnet 94B in which a plurality of magnetic poles is locatednext to one another in the circumferential direction as shown in FIG.24. In this case, the recess 86A of the base 92 is annular. In a casewhere the base 92 of FIG. 23 includes a magnetic material, the base 92can be magnetized to form the magnetism generation portion 94.

As shown in FIGS. 25 and 26, the attaching portion 26 of the adaptermain body 22 can be provided on one of the projections 36 instead ofbeing provided between two of the projections 36 that are adjacent toeach other in the circumferential direction. The attaching portion 26 isformed integrally with the projection 36.

The thermal insulation portion 28 can be omitted from each of the firstand third to eighth embodiments and the modifications.

The adapter main body 22 of each of the embodiments and modificationscan include a heat dissipation portion. The heat dissipation portionincludes, for example, one or more fins. It is preferred that the heatdissipation portion be provided in the vicinity of the magnetismgeneration portion 24. The heat dissipation portion is provided, forexample, on a surface of the adapter main body 22 opposite to themagnetism generation portion 24 in the axial direction at a positionoverlapping the magnetism generation portion 24 as viewed in the axialdirection.

As shown in FIG. 27, in a state where the disc brake rotor 10 is coupledto the hub H, the holder 50 of the third embodiment can be located at aside opposite to the second end H6 of the hub shell H1 of the hub H. Ina state where the disc brake rotor 10 is coupled to the hub H, theopening of the recess 50A is formed at the side opposite to the secondend H6 of the hub shell H1 of the hub H. The attaching portion 48 isinserted into the first hole 36A and fixed to the projection 36. Thejoining portion 54 has a second end 54B, which is inserted through thethrough hole 50B and located in the cavity of the recess 50A. The holder50 is held between the projection 36 and a portion of the second end 54Blocated in the cavity of the recess 50A. This supports the holder 50.

As shown in FIG. 28, the disc brake rotor 10 of each of the embodimentsand modifications can be changed to a disc brake rotor 10A, which isconfigured so that the main body 12 is attachable to and removable fromthe adapters 20A to 20H. The disc brake rotor 10A that is shown in FIG.28 includes, for example, a plurality of through holes 102 extendingthrough the main body 12. The through holes 102 are located in positionscorresponding to the first holes 36A (refer to FIG. 3). A first spacerS1 and a second spacer S2 are located between the fixing member R andthe main body 12. The attaching portion 26 is formed integrally with theadapter main body 22. In another example, the attaching portion 26 isformed separately from the adapter main body 22 and coupled to theadapter main body 22 so that the attaching portion 26 is attachable toand removable from the adapter main body 22.

The attaching portion 42 of the second embodiment can be modified sothat the attaching portion 42 is provided on a first side surface 110Aof a disc brake rotor 110. For example, the disc brake rotor 110 that isshown in FIG. 29 includes a hub connector 112, a main body 114, and arms116. The hub connector 112 is configured to be coupled to the hub H(refer to FIG. 2) of the bicycle. The arms 116 connect the hub connector112 and the main body 114. The disc brake rotor 110 includes a pluralityof arms 116. The combination of the hub connector 112 and the arms 116has the same structure as the adapters 20A to 20H of the aboveembodiments. The hub connector 112 corresponds to the inner portion 32of the adapters 20A to 20H of the above embodiments. The arms 116correspond to the projections 36 of the outer portion 34 of the aboveembodiments. The main body 114 is located at a radially outer side ofthe hub connector 112. The disc brake rotor 110 includes the first sidesurface 110A and a second side surface 110B. In a state where the discbrake rotor 110 is coupled to the hub H, the second side surface 110B islocated closer to the second end H6 of the hub shell H1 of the hub H.The first side surface 110A is opposite to the second side surface 110Bin the axial direction. The main body 114 has the same structure as themain body 12 of the disc brake rotor 10 of the above embodiments. Inthis modified example, the hub connector 112 can be formed integrallywith the arms 116. Alternatively, the hub connector 112 can be formedseparately from the arms 116. Additionally, the arms 116 can be formedintegrally with the main body 114. Alternatively, the arms 116 can beformed separately from the main body 114. As shown in FIG. 30, amagnetism generation device 120 is attachable to the disc brake rotor110. The magnetism generation device 120 includes the magnetismgeneration portion 24, a holder 124, and a third coupling portion 126.The holder 124 holds the magnetism generation portion 24. The magnetismgeneration portion 24 is embedded in the holder 124. The third couplingportion 126 is formed integrally with the holder 124 and attachable tothe first side surface 110A of the disc brake rotor 110 in the axialdirection. The holder 124 is formed from a low permeability material andincludes, for example, a resin. The third coupling portion 126 isattached to the first side surface 110A, for example, by a bolt or anadhesive. The third coupling portion 126 is attached to the main body114 of the disc brake rotor 110.

The holder 124 is configured so that at least a portion of the magnetismgeneration portion 24 projects from the first side surface 110A into acavity 125 defined by adjacent ones of the arms 116 of the disc brakerotor 110 in a state where the third coupling portion 126 is attached tothe first side surface 110A. The third coupling portion 126 includes afirst part 126A and a second part 126B. The first part 126A includes ahole 127, which is internally threaded. The holder 124 is provided on anaxial end of the second part 126B. The holder 124 projects from thethird coupling portion 126 in the axial direction. In the example shownin FIG. 29, in a state where the third coupling portion 126 is attachedto the disc brake rotor 110, the first part 126A is located at aradially outer part of the third coupling portion 126, and the secondpart 126B is located at a radially inner part of the third couplingportion 126.

The third coupling portion 126 of FIG. 30 can be attached to the firstside surface 110A on the adapter main body 22. For example, the hole 127extends through the third coupling portion 126 in the axial direction. Abolt B1 is inserted through the hole 127 and fastened to a threaded holeformed in the adapter main body 22. This fixes the holder 124 to thedisc brake rotor 110.

The attaching portion 42 of the second embodiment or the holder 124 ofFIG. 29 can be attached to a disc brake rotor 10B that is shown in FIG.31. The disc brake rotor 10B includes a plurality of first couplingportions 13A, a second coupling portion 13B, the magnetism generationportion 24, and the holder 124. The first coupling portions 13A areattachable to the hub H of the bicycle by bolts B. The first couplingportions 13A extend through in the axial direction. The projection H5(refer to FIG. 2) of the hub H includes internal threads, to which theexternal threads of the bolts B are fastened. Each of the first couplingportions 13A includes a through hole. The first coupling portions 13Aare located on the disc brake rotor 10A at positions corresponding tothe internal threads formed in the projection H5 of the hub H. Thesecond coupling portion 13B and the first coupling portions 13A areprovided at different positions. A through hole extends through thesecond coupling portion 13B in the axial direction. The holder 124couples the magnetism generation portion 24 to the second couplingportion 13B so that the magnetism generation portion 24 is attachable toand removable from the second coupling portion 13B. The holder 124corresponds to an attaching portion. The second spacer S2 is locatedbetween the disc brake rotor 10A and the heads of the bolts B. The boltB1 is extended through the second coupling portion 13B and fastened tothe internal threads of the third coupling portion 126 of the holder124. This couples the holder 124 to the disc brake rotor 10B so that theholder 124 is attachable to and removable from the disc brake rotor 10B.In the example shown in FIG. 31, in a state where the third couplingportion 126 is attached to the disc brake rotor 110, the first part 126Ais located at a radially outer part of the third coupling portion 126,and the second part 126B is located at a radially inner part of thethird coupling portion 126.

The magnetism generation portions 24, 94 of the embodiments can includean electromagnet instead of or in addition to the permanent magnet. Inthis case, the magnetism generation portions 24, 94 can include a coiland a battery that supplies power to the coil. In a case where themagnetism generation portions 24, 94 include an electromagnet, a dynamocan be provided on the hub H so that power is supplied from the dynamo.

The recesses 38A, 44A, 50A, 58A, 64A, 86A can be omitted from the firstto fifth embodiments and the modifications. The magnetism generationportion 24 and the thermal insulation portion 28 can be provided on asurface of each of the holders 38, 44, 50, 58, 64, 86.

In each of the embodiments and modifications, the magnetism generationportions 24, 94 can be embedded in the holders 38, 44, 50, 58, 64, 72,86. In this case, the holders 38, 44, 50, 58, 64, 72, 86 are formed, forexample, from a resin material. The magnetism generation portions 24, 94are formed integrally with the holders 38, 44, 50, 58, 64, 72, 86.

In each of the embodiments and modifications, in a state where themagnetism generation portion 24 is accommodated in the recesses 38A,44A, 50A, 58A, 64A, 76A, 86A, the magnetism generation portion 24 can becovered by a cover member so as not to be exposed from the openings ofthe recesses 38A, 44A, 50A, 58A, 64A, 76A, 86A. The cover member isformed from a low permeability material and includes, for example, aresin or an aluminum alloy. The cover member can be fixed to at leastone of the adapter main body 22 and the magnetism generation portion 24through adhesion, fusing, or welding or by a screw.

In each of the embodiments and modifications, the attaching portions 26,42, 48, 56, 62, 70, 84, 90 can be located between the adapter main body22 and the main bodies 12 of the disc brake rotors 10, 10A, between thehub connector 112 of the disc brake rotor 110 and the hub H, or betweenthe adapter main body 22 and the first end H4 of the hub H. In thiscase, a groove or a step is formed on a surface of the adapter main body22 located closer the hub H. The attaching portions 26, 42, 48, 56, 62,70, 84, 90 are engaged with the groove or the step to attach themagnetism generation portions 24, 94 to the adapter main bodies 22.

What is claimed is:
 1. A magnetism generation device attachable to adisc brake rotor adapter for a bicycle hub, the magnetism generationdevice comprising: a magnetism generation portion; a holder having afirst portion and a second portion, the first portion supports themagnetism generation portion, the second portion being attached to thefirst portion with a portion of the disc brake rotor adapter disposedbetween the first and second portions in an axial direction that isparallel to a center rotational axis of the bicycle hub while themagnetism generation device is in an installed state on the disc brakerotor adapter, the magnetism generation portion overlapping with thebrake rotor adapter in the axial direction while the magnetismgeneration device is in the installed state on the disc brake rotoradapter; a first fastener having a shaft portion extending parallel toan axis of rotation of the disc brake rotor adapter, the first fastenerattaching the first and second portions together; and a second fastenerhaving a shaft portion extending parallel to the axis of rotation of thedisc brake rotor adapter, the second fastener attaching the first andsecond portions together, the magnetism generation portion beingdisposed circumferentially between the first and second fasteners withrespect to a center rotational axis of the bicycle hub in a state inwhich the magnetism generation device is attached to the bicycle hub bythe disc brake rotor adapter in which the magnetism generation device isattached to the bicycle hub by the disc brake rotor, wherein the firstand second fasteners are spaced from the disc brake rotor adapter. 2.The magnetism generation device according to claim 1, wherein the firstportion includes an opening in which the magnetism generation portion isdisposed.
 3. The magnetism generation device according to claim 2,wherein the opening is disposed on a surface of the first portion thatfaces in a direction away from the bicycle hub while the magnetismgeneration device is in the installed state on the disc brake rotoradapter.
 4. The magnetism generation device according to claim 1,wherein the first fastener includes a bolt.
 5. The magnetism generationdevice according to claim 1, wherein the second fastener includes abolt.
 6. The magnetism generation device according to claim 1, whereinat least one of the first and second portions includes a through holefor receiving the first fastener.
 7. The magnetism generation deviceaccording to claim 1, wherein one of the first and second portionsincludes a pair of through holes for receiving the first and secondfasteners, the other of the first and second portions includes a pair ofopenings that are aligned with the through holes for receiving the firstand second fasteners.
 8. The magnetism generation device according toclaim 7, wherein the openings are threaded for threadedly receiving thefirst and second fasteners.
 9. The magnetism generation device accordingto claim 1, wherein the first and second portions are configured to beattached to the disc brake rotor adapter in a manner irrelevant to afixing function of a fixing member that is configured to fix the adapterto the bicycle hub.
 10. The magnetism generation device according toclaim 9, wherein the first and second portions are configured to beattachable to and removable from the brake rotor adapter.
 11. Themagnetism generation device according to claim 1, wherein the magnetismgeneration portion includes at least one permanent magnet.
 12. Themagnetism generation device according to claim 1, wherein the first andsecond fasteners are arranged such that a radially extending projectionof the disc brake rotor adapter is disposed between the first and secondfasteners while the magnetism generation device is in the installedstate on the disc brake rotor adapter.
 13. The magnetism generationdevice according to claim 12, wherein the magnetism generation portionis aligned with the projection of the disc brake rotor adapter in anaxial direction of the disc brake adapter while the magnetism generationdevice is in the installed state on the disc brake rotor adapter.
 14. Amagnetism generation device attachable to a disc brake rotor adapter fora bicycle hub, the magnetism generation device comprising: a magnetismgeneration portion; and an attaching portion that supports the magnetismgeneration portion, the attaching portion including a recess in whichthe magnetism generation portion is disposed, the recess having anopening disposed on a surface of the attaching portion that faces in adirection away from the bicycle hub while the magnetism generationdevice is in the installed state on the disc brake rotor adapter, theattaching portion including a holder, the holder having a first portionand a second portion, the first portion supports the magnetismgeneration portion, the second portion being attached to the firstportion with a portion of the disc brake rotor adapter disposed betweenthe first and second portions in an axial direction that is parallel toa center rotational axis of the bicycle hub while the magnetismgeneration device is in an installed state on the disc brake rotoradapter, the magnetism generation portion overlapping with the brakerotor adapter in the axial direction while the magnetism generationdevice is in the installed state on the disc brake rotor adapter; and afastener having a shaft portion extending parallel to an axis ofrotation of the disc brake rotor adapter, the fastener directly securingthe attaching portion on a portion of the disc brake rotor adapter whilethe magnetism generation device is in an installed state on the discbrake rotor adapter while the magnetism generation device is in aninstalled state on the disc brake rotor, wherein the fastener is spacedfrom the disc brake rotor adapter.
 15. The magnetism generation deviceaccording to claim 14, wherein the magnetism generation portion includesat least one permanent magnet.
 16. The magnetism generation deviceaccording to claim 15, wherein the magnetism generation portion includesa plurality of permanent magnets spaced apart from one another on theattaching portion in a circumferential direction.
 17. The magnetismgeneration device according to claim 14, wherein the fastener includes abolt.
 18. The magnetism generation device according to claim 14, whereinthe attaching portion includes a through hole for receiving thefastener.